Perfumes are used in many applications to mask malodours. A particularly important category of malodours are, for example, those resulting from substances transpired by or excreted by humans in particular perspiration, urine, faeces or menstrual fluid, and odours caused by animal urine or faeces, especially those of domestic pets.
Malodours are usually caused by particularly odorous substances such as sulphur compounds e.g. hydrogen sulphide, and low molecular weight thiols and thioethers, nitrogen containing compounds such as ammonia and amines including heterocyclic compounds such as pyrazines and indoles, oxygen containing compounds such as fatty acids and steroids. These malodorous compounds are often created by the action of micro-organisms on excreted material or during the digestion of food or drink. As natural products the malodours are themselves complex mixtures, not only of several compounds within each of the above categories but also including members of all the categories to different degrees depending on the source of the odour. Consequently preventing, countering, reducing or destroying malodour is not straightforward.
Various methods have been developed to counter or reduce malodour beyond odour masking with strong fragrance. Activated carbon and zeolites have been used as absorbents for malodours but these are not suited for incorporation into many products. Antimicrobial agents such as zinc compounds and Triclosan (2′,4′,4′-trichloro-2-hydroxy-diphenyl ether) are used to kill microorganisms involved in producing malodours, but many are non-specific and can lead to imbalances in the natural microflora.
U.S. Pat. Nos. 4,304,679; 4,322,308; 4,278,658 and 4,134,838 all describe fragrances which exhibit a deodorant action when applied to human skin or when included in a laundry product. These are believed to work by any or all of a variety of mechanisms: reducing the vapour pressure of malodorous compounds, inhibiting the enzymes which generate the malodours and combining with the malodour to modify the perceived odour note.
U.S. Pat. No. 4,719,105 describes the use of cyclomethanols and esters as low odour materials which can be used to mask malodours without having unduly strong fragrances themselves.
US patent application 2004/0147416 describes the use of cyclodextrins to trap malodorous molecules.
Malodours tend to become stronger over time as the population of micro-organisms grows and malodour production increases. Herein lies a major disadvantage of using perfumes to mask malodour. While a perfume can mask a malodour just after application, over time the intensity of the fragrance decreases, whereas the malodour will in all probability increase in intensity from the growing micro-organism colonies. The same argument can be applied equally well to counteractants which work by reacting with malodorous molecules, in time they will be overwhelmed by the malodours. Their effect is to delay or reduce the intensity of the malodour and as such this may be sufficient for some commercial applications.
A different approach is to inhibit specific biological pathways. Compounds which act more specifically include saturated C3-C10 dioic acids which inhibit a sweat decomposing esterase as described in DE patent application 4,343,265.
U.S. Pat. No. 6,183,731 describes the use of agents which are inhibitors of 5α-reductase, such as octadecendioic acid as a preventative agent for body malodour.
U.S. Pat. No. 5,395,555 teaches an aqueous cleaning composition for carpets, rugs, and textiles, particularly useful in reducing malodour of urine stains containing selected metal sequestrants which is thought to deny heavy metals essential to the micro-organisms' development.
However as mentioned earlier malodours are complex and such approaches may not counter all the components of the malodour, so it is more likely that they modify the nature of the odour which again may be a worthwhile benefit but is only a partial solution to the problem.
Aldehydes are sometimes cited as malodour counteractants. U.S. Pat. No. 4,906,454 describes piroctone acid and a perfume with a high concentration of aldehydes and/or ketones for use in deodorants in preventing body malodours. U.S. Pat. No. 6,177,070 describes a deodorant product containing at least two different aldehydes present in the form of addition compounds such as acetals and hemi-acetals and an unsaturated compound. This is quite different from the aldehydes in the present invention which are not present as addition compounds but comprise part of the fragrance added directly to the product.
US patent application 2005/0124512 describes the use of fabric safe aldehydes (i.e. non discolouring) as components of air or fabric freshening spray products which react with malodorous components in air. There is nothing in this patent which teaches that the aldehydes might inhibit odour formation especially that they might do so in a non reactive way which leaves the fragrance unimpaired.
U.S. Pat. No. 5,676,163 describes two classes of aldehydes which act additively or synergistically to reduce the malodour of tobacco smoke. Again the patent only teaches that aldehydes react with some malodorous molecules and there is no evidence for the prevention of biologically generated malodours.
US patent applications 2005/1087123 and 2005/0187124 describe compositions to be incorporated into solid and liquid carpet cleaner and de-odourising products to remove malodours from carpets. In US patent application 2005/0187123 aldehydes are optional components of the mixture and there is no teaching beyond their having an odour reaction and masking effect. However in co-filed US patent application 2005/187124 aldehydes are described as enzyme inhibitors whilst aldehydes and ketones are described as odour reactants. No evidence is given as to which enzymes are inhibited or which malodorous compounds reduced or prevented and only benzaldehyde would be considered as a fragrance aldehyde among the group of aldehydes cited and the efficacy of benzaldehyde is not demonstrated in the examples.
US patent application 2002/0010447 describes two categories of aldehydes for malodour reduction in fibrous absorbents for bodily fluids. The categories of aldehydes which are claimed to work synergistically are aliphatic aldehydes and aldehydes which have an sp2 hybridised carbon in the alpha position to the aldehyde carbon. Again there is nothing in the text to suggest that the aldehydes have any inhibitory effect beyond chemical reaction or vapour pressure reduction.
US patent application 2003/0044309 describes mixtures of two types of aldehydes for malodour counteraction in carpet cleaners but all of the examples described intimate mixing of the test formulation with the malodour source allowing for chemical reaction. Nowhere does the document suggest that indole based malodours might be prevented.
From all of the prior art references and examples, aldehydes with the specific exception of formaldehyde are predominantly considered to work by chemical reaction with a pre-existing odorant rather than the specific prevention of indole based malodours. Formaldehyde is well known as an antimicrobial agent which is frequently incorporated into formulations directly or in the form of any of several derivatives which release formaldehyde slowly.
Thus while it is apparent from the prior art that there are many methods which attempt to prevent malodour, none are completely satisfactory. The present invention describes a simple and inexpensive way to prevent the development of some of the components of urinous or fecal malodours via specific ingredient selection within the fragrance incorporated into a wide range of household and personal care products.